Self-Healing Polymer Could Be Key to Longer-Lasting Batteries

A couple of months ago, we told you about a so-called Terminator polymer that could heal itself. Now, researchers at Stanford University are using a similar material to improve the durability of lithium-ion batteries so they don’t crack under the pressure of use.

Researchers in Stanford’s and the Department of Energy’s SLAC National Accelerator Laboratory have developed a conductive self-healing polymer and used it to coat the electrode of a battery, which binds the electrode together and spontaneously heals tiny cracks that develop during battery operation.

This makes the battery more durable and able to withstand more charge and discharge cycles, lasting 10 times longer in tests in the lab than typical lithium-ion batteries, Chao Wang, a post-doctoral researcher working on the project, told Design News, in an email.

Stanford postdoctoral researcher Chao Wang holds a solid piece of the stretchy, self-healing polymer used to coat and protect silicon battery electrodes. Wang and colleagues at Stanford developed the polymer to help increase the lifetime of the batteries so if they crack under the pressure of use they can repair themselves. (Source: Brad Plummer/SLAC National Accelerator Laboratory)

The benefit of using self-heal polymer is that the mechanical failures inside the battery can self-heal at the same time, maintaining the electrical and mechanical contact of the materials. In this way, the decay of the capacity can be much slower. We don't need to change the chemistry of the battery. The self-healing polymer composite serves as a coating on the active materials.

Wang -- who developed the polymer and coating method with Professor Zhenan Bao -- said the inspiration for the work comes from nature, pointing out the ability humans have to heal once we’ve been injured. However, existing self-healing polymers to date have not been conductive, which required Bao, Wang, and their team to modify a self-healing material that already existed by adding tiny nanoparticles of carbon to the polymer, Wang said.

We want to make the self-healing materials with electrical property, so we modified a previously known self-healing polymer, tuned the mechanical properties according to our need, and made it conductive. It can self-heal because it has a lot of hydrogen bonds, which are weak and reversible. So when there are mechanical damages, these hydrogen bonds will break first instead of covalent bonds. The hydrogen bonds will reversibly form and self-heal when the damaged interfaces get in touch again.

Wang and Hui Wu, a former Stanford postdoc who is now a faculty member at Tsinghua University in Beijing, co-authored a paper about their research in a recent article in Nature Chemistry.

Indeed, researchers have been trying a number of ways to create longer-lasting batteries for myriad devices and in particular electric vehicles (EVs), which still lack a viable battery that lasts long enough to go long distances without being recharged. Battery lifetime is also an issue for electronic devices like smartphones, as researchers seek ways to make batteries not only last longer before needing a recharge but also have a longer life span in general.

Many research efforts under way are experimenting with battery chemistries, trading ion for air in lithium-based batteries or trying a new spin on old chemistries, such as lead-acid batteries. The Stanford effort appears to be one of the first to find a new way to improve lithium-ion batteries not by altering the chemistry itself but by adding this self-healing property.

Wang said the next step for the research is to increase the battery’s lifetime even further and to apply the self-healing concept to other batteries besides lithium-ion. However, while the concept is promising to the future of batteries, it will likely be some time -- at least five to 10 years -- before this technology might be commercially available.

Yes, I agree with you, Rob, but you know how long it can take for these things to leave the lab--I think we'll be lucky if we get this in that time frame! It does seem like incredibly useful technology, though, and could be the key to better batteries.

Yes, I think in terms of big-ticket or popular products like consumer devices, this isn't such a problem anymore because there is a lot of competition pushing companies to get the best product out the first time around. But with batteries especially in terms of all of the experimentation happening, there might be a bit of an adoption curve before the technology is mature.

This reminds me of self sealing gas tanks on planes. The technology was invented in 1921, but pretty much languished in the post WWI era. When WWII started, the application's value became extremely apparent; Allied planes started having the self sealing tanks installed by 1942 and continue to this day. The difference is an immediate need today. I hope this accelerates acceptance by battery manufacturers.

That's true, shehan, and what I think is most interesting about this is that while other scientists are working on new chemistries to make batteries last longer, this actually affects the structure of the battery and not the chemistry. It seems also like too easy of a fix for a problem that has been until now seemingly complicated to solve. I guess time will tell.

@far911- At times I tend to think that battery manufacturers have not invested much time and money on research and development. A battery manufacturer surely knows in an out of the batteries they manufacture and the materials used.

"At times I tend to think that battery manufacturers have not invested much time and money on research and development. A battery manufacturer surely knows in an out of the batteries they manufacture and the materials used."

Shehan, how does it matter? Everybody is using the same cells with same technology and material.

"The Stanford effort appears to be one of the first to find a new way to improve lithium-ion batteries not by altering the chemistry itself but by adding this self-healing property."

It makes me wonder what studies have been done to conclude that the number of effective charging cycles are reduced because of broken connections versus the battery chemistry itself losing its potential through extended use. While I applaud the concept and can see how it would be helpful when these conditions occur, I don't know enough to understand if this is really a valid solution for general battery use or just a specific failure mode among others. Regardless, the technology is amazing and I admire the work of these researchers - we may very well find some spin-off applications from this research.

I say it will be great to have batteries lasting long while in use, and every one seems 2 be kken 2 see it soon , same goes for me as it will be great not to keep many batteries in resrve for the games, remote , kids toys etc.so looking forward for a rapid development.

@far911- If you think of the applications what not can you use it for? Imagine using this technology to power vehicles. You could drive miles with just a single charge. That's when we really make use of this technology.

Elizabeth, now a day's peoples are using more and more gadgets in day to day life. So I personally feel the requirement of some mechanism to increase the life time of batteries rather than such self healing technologies.

"yes most people use gadgets such as tablets, media players etc. every day. It's always nice to see a long lasting battery."

Shehan, such technologies are yet to be developed. As of now most of such gadgets cells are in range of 1800-2500mAh. Iof they are able to come up with 5000mAh range cells, it may last long. But I don't know, what's the reason still manufacturers are not looking to such aspects.

That's a really good point, Mydesign. I think this self-healing effort is a good one as well, though, because it will help these batteries last longer in general so they don't have to be replaced. Some people have argued that it's not often long-lasting batteries are replaced but I beg to differ. But you're right, to increase the actual usage time of a battery--ie, how long it holds its charge--is probably an even more important aspect of batteries to be working on.

For those of us who work in the design of electronic products, this development is ground breaking and could change or overhaul most of the designs that are currently in the market since it answers one of the biggest headaches in this field; how to ensure lifetime power supply is provided for special components of the device.

On second thought, the fact that there a 'terminator polymer' with conducting properties of its own is yet to be developed still means that it may be a while before large scale use of the new batteries is witnessed. This is because the creation of the current polymer developed by the Stanford team also includes additional costs for the addition of carbon nanoparticles, a fact that will definitely make them more expensive.

"The other day I saw a video on these self healing materials, and I was amazed by this invention. Certainly it can find numerous applications in the engineering world specially in the polymer industry."

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